Equations · equation

Snell's Law

Waves & Optics · 984

Equation: n₁·sin θ₁ = n₂·sin θ₂
Field: Waves & Optics
Named After: Ibn Sahl · Willebrord Snellius
Symbols: n₁, n₂ refractive indices of the two media · θ₁, θ₂ angles of the ray from the surface normal on each side
Year: 984

Significance

Light bends when it crosses into a new medium — the rule behind every lens, eyeglass, camera, and the total internal reflection that traps light inside optical fibers. First stated by Ibn Sahl in Baghdad in 984, rediscovered by Snellius in 1621, and it's why pools look shallower than they are.

Minerals

Fluorite Diamond Cryolite Quartz Calcite

Theories

Corpuscular Theory of Light Wave Theory of Light

Related

Gaussian Beam Divergence Plasma Frequency

Instruments

Very Large Telescope (VLT)

Requires

Trigonometric Ratios Refractive Index

Elements

Referenced by

element

equation

Gaussian Beam Divergence Plasma Frequency Refractive Index Trigonometric Ratios

instrument

Very Large Telescope (VLT)

theory

Corpuscular Theory of Light Wave Theory of Light

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From the Equations database in Notion, last edited 2026-08-18. This page is the row, rendered by the build; nothing on it is written by hand.